Device, process, and catalyst intended for desulfurization and demercaptanization of gaseous hydrocarbons

ABSTRACT

The invention is related to the sphere technologies for desulfurization and demercaptanization of gaseous hydrocarbons. It can be used for purification of any gaseous hydrocarbon medium. The device includes a catalytic reactor loaded with a catalyst solution in an organic solvent, a means of withdrawal sulfur solution from the reactor into the sulfur-separating unit, and a sulfur-separating unit. The sulfur-separation unit includes a means of sulfur extraction. The reactor design and the catalyst composition provide conversion of at least 99.99% of hydrogen sulfide and mercaptans into sulfur and disulfides. The catalyst is composed of mixed-ligand complexes of transition metals. The technical result achieved by use of claimed invention is effectively a single-stage purification of gaseous hydrocarbons from hydrogen sulfide and mercaptans with remaining concentration of —SH down to 0.001 ppm while leaving no toxic waste.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent application is a continuation-in-part of the U.S.patent application Ser. No. 16/222,344 filed Dec. 17, 2018, which claimspriority to U.S. patent application Ser. No. 15/539,867 filed Jun. 26,2017, which is the National stage patent application from PCTapplication PCT/RU2016/000415 filed Jul. 4, 2016, which claims priorityto Russian patent application RU2016116049 filed Apr. 25, 2016, all ofwhich incorporated herein by reference in their entirety.

FIELD OF INVENTION

This application is in sphere of technologies for desulfurization anddemercaptanization of raw gaseous hydrocarbons (including natural gas,tail gas, technological gas, etc). It can be used for desulfurizationand demercaptanization of any kind of raw gaseous hydrocarbons.

BACKGROUND

A prior art (RU patent No. 2394635, issued. 20 Jul. 2010) discloses aprocess for desulfurization and demercaptanization of gas based onabsorption method. The gases to be purified are pressurized, and treatedby two absorbing agents, first by water solution of neutral sodium saltsof hydrosulfuric acid and of carbonic acid, and then by water solutionof sodium hydroxide.

The same prior art describes a device for desulfurization anddemercaptanization of gas as well as removal of carbon dioxide and otheracidic additives, that includes two absorbers, each of them includes astorage vessel to hold absorbing agent and a pump that provides meteredflow of absorbing agent into the absorber, where the second absorber,relatively to gas flow direction, contains solution of sodium hydroxide,and exhaust collecting vessels to collect exhaust absorbing agents. Theabsorbers are connected in a cascade; they are pressurized; the secondabsorber is equipped with a circulation pump; the exhaust collectingvessel of the first absorber is connected with a charging pump that isused to dump exhaust absorbing agent into isolated chambers, where as anabsorbing agent in the first absorber, water and exhaust absorbing agentfrom the second absorber are used; additionally, the said deviceincludes a compressor that maintains required pressure of the gas to bepurified, and a separator that is connected to the said compressor, thatis used to remove gas condensate and water.

As drawbacks of the said prior art, the following must be admitted: lowpurification performance, high alkali discharge rate, generation of ahigh amount of toxic waste that is hard to dispose of.

A prior art (U.S. Pat. No. 4,622,212, issued 11 Nov. 1986) describes aprocess of liquid-state oxidation of hydrogen sulfide to sulfur by meansof chelating complexes of iron (Lo-Cat process). In the Lo-Cat process,a catalytic reactor for conversion of hydrogen sulfide into sulfur isused, and a device to regenerate the catalyst solution.

The said process features insufficient degree of desulfurization andincapability of demercaptanization that must be admitted as itsdrawbacks.

A prior art (U.S. Pat. No. 8,735,316, issued. 27 May 2014) describes aprocess of catalytic demercaptanization by converting mercaptans todisulfides. As a catalyst, the complex CuCl with monoethanol amine(MEA), acetonitrile, or with a monobasic alcohol is used. The processflows in presence of air oxygen, at a temperature of 22-140° C. Theresidual amount of mercaptan sulfur can be reduced to 20 ppm.

The said process is capable of purifying only liquid media, and no datais provided concerning its capability of hydrogen sulfide removal, thatmust be admitted as the drawbacks.

A prior art (RU patent No. 2385180 issued. 27 Mar. 2010) describes aClaus-process of obtaining sulfur from hydrogen sulfide by means ofcatalytic reaction of hydrogen sulfide and sulfur dioxide.

The said art features primary amine treatment of the gas to be purified,multiple stages of the process and insufficient conversion of hydrogensulfide to sulfur, necessity of tail gas treatment, sophisticatedtechnological equipment, and incapability of demercaptanization, allthese items must be admitted as the drawbacks.

A prior art (U.S. Pat. No. 5,286,697, issued 15 Feb. 1994) alsodescribes an improved Claus process.

The said art is also incapable of demercaptanization, and it is lessefficient in hydrogen sulfide conversion.

A prior art (RU patent No. 2405738, issued 27 Apr. 2010) describes aprocess of sulfur recovery from industrial gases by means of a catalystthat contains on dehydroxylated silica gel (97.65% by mass) impregnatedwith ferric phosphate (III) (2.35%), that provides sulfur formation fromhydrogen sulfide.

The said art features insufficient conversion of hydrogen sulfide, andcatalyst production complexity, that must be admitted as drawbacks.

A prior art (RU patent No. 2398735, issued 10 Sep. 2010) describes ameans of gas desulfurization by oxidating hydrogen sulfide to elementalsulfur in liquid state in presence of a catalyst, which contains acompound of a transition metal and an organic complexing agent. Tooxidate hydrogen sulfide, it is proposed to use air oxygen as oxidizer;as a compound of transition metal, cupric halogenide is used, where theamount of copper in the solution is 0.015 to 0.1% by weight, and whereas an organic complexing agents, one of the following is used:dimethylformamide, pyrrolidone, methylpyrrolidone, pyridine, orquinolone; the process flows in a solvent that is taken as one of thefollowing: monobasic alcohol, polybasic alcohol, water, or theirmixtures, kerosene, isooctane, gas condensate at temperature of 20-40°C.

The drawback of the said process is its mediocre efficiency.

SUMMARY

The technical problem that is solved by means of the proposed inventionis to develop an engineering solution that provides desulfurization anddemercaptanization with conversion over 99.999%.

The technical result achieved by use of the proposed engineeringsolution is a single-stage desulfurization/demercaptanization withresidual amount of —SH down to 0.001 ppm while producing no toxic waste.

To achieve the said technical result, it is proposed to use a device(FIG. 1) and a process (FIG. 2) for desulfurization anddemercaptanization of gaseous hydrocarbons, and a catalyst for efficientuse of the said process. The proposed device includes a catalyticreactor loaded with a catalyst for H₂S and RSH oxidation into sulfur anddisulfides respectively in an organic solvent, an apparatus forwithdrawal sulfur solution from the reactor to sulfur separation block,and a sulfur separation block, where the device includes at least ameans of supplying gas to be purified and oxygen-containing gas into thereactor, a means of outputting the purified gas from the reactor; andwhere the sulfur separation block includes a means of sulfursegregation; and where the reactor design and catalyst compositionprovides conversion of at least 99.99% of hydrogen sulfide andmercaptans to sulfur and disulfides; and where the catalyst is composedof mixed-ligand complexes of transition metals.

While the gas is passed through the catalyst solution, hydrogen sulfideand mercaptans are converted into sulfur and disulfides in accordancewith reaction:

H₂S+2RSH+O₂═S+RSSR+2H₂O  (1)

The purified gas is given out to the end user from the reactor outlet.The disulfides formed in reaction (1) remain in the reactor, and they donot affect the main process in any way. The water that evolves inreaction (1) is partially withdrawn from the reactor together with thepurified gas, and partially—with fine sulfur suspension.

Fine sulfur suspension is withdrawn from the reactor intosulfur-separating unit. The sulfur-separation unit may include a meansof sulfur separation from the solution with solution recycling into thereactor thereafter.

The device may additionally include a unit for homogenization of mixtureof the gas to be purified with the oxygen-containing gas.

The reactor should preferably include a means of distribution of thesupplied gas to be purified in the volume of the reactor, or fillingplates.

The device may additionally include a means of metered supply of thecatalyst.

As a catalyst, the device should preferably use mixed-ligand complexesbased on ferric and/or cupric halogenides.

To achieve stated technical result, the developed process ofpurification of gaseous hydrocarbons from hydrogen sulfide andmercaptans may also be used.

According to the developed process, the raw gas to be purified is mixedwith the oxygen-containing gas and passed through the reactor withorganic solution of the catalyst that provides conversion of at least99.99% of hydrogen sulfide and mercaptans into sulfur and disulfides,and where the catalyst is mixed-ligand complexes of transition metals.

The temperature in the device is preferably to be kept in range of20-140° C.

In the described process embodiment, typically the amount of oxygen istaken not less than 50% of total amount of hydrogen sulfide andmercaptan sulfur.

The gas mixture supplied into the reactor is preferably to be evenlydistributed in the reactor volume.

In the described process implementation, typically metered supply of thecatalyst into the device is used, while the sulfur is separated from thesuspension, and the solution is recycled into the reactor.

Typically, a catalyst is used that consists of mixed-ligand complexes offerric and/or cupric halogenides.

Also, to achieve the stated technical result it is suggested to use thecatalyst for desulfurization and demercaptanization of gaseoushydrocarbons that has the proposed composition. The said catalyst is a0.0001-100% solution of ferric chloride and/or cupric chloride, amine,and amide, taken in a ratio of 1:20-1:0.1, in alcohol.

In the catalyst, preferably as amines, benzyl amine, cyclohexilamine,pyridine, and as amide-dimethylformamide are used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the block diagram of the proposed device in the preferredembodiment

FIG. 2 shows the process according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows the block diagram of the proposed device in the preferredembodiment, where the following notations are used: inlet pipe 1 thatsupplies raw medium to be purified, mixing unit 2 that mixes hydrocarbongas to be purified with oxygen-containing gas, inlet pipe 3 thatsupplies oxygen-containing gas, agitator 4 of oxygen-containing gasdischarge, pipe 5 that supplies mixture of hydrocarbon gas to bepurified with oxygen-containing gas, catalytic reactor 6, means 7 ofdistribution of mixture of hydrocarbon gas and oxygen-containing gas inthe volume of reactor 6 or filling plates, tank 8 containing catalystsolution, agitator 9 of metered supply of catalyst solution from tank 8into reactor 6, pipe 10 that supplies catalyst solution into reactor 6,pipe 11 that outlets purified gas, pipe 12 that outlets sulfursuspension into sulfur-separating unit 13, pipe 14 of sulfur outlet fromsulfur-separating unit 13, pipe 15 that outlets catalyst solution fromsulfur-separating unit 13 into catalytic reactor 6 after sulfur has beenseparated, agitator 16 of catalyst solution recycling fromsulfur-separating unit 13 into catalytic reactor 6. The general stagesor the process realization are shown in FIG. 2, where the followingnotation is used: supplying raw hydrocarbon material mixed withoxygen-containing gas to the reactor—17, passing the raw materialthrough the reactor loaded with an organic solution of the catalyst—18,output of pure gas from the reactor, where the conversion of hydrogensulfide and mercaptans to sulfur and disulfides is 99.99% —19, usage ofoxygen, not less than 50% of total amount of hydrogen sulfide andmercaptan sulfur—20, distribution of gas mixture evenly in the reactorvolume—21, metered supply of the catalyst into the reactor—22,separation of sulfur from the suspension and recycling of catalystsolution into the reactor—23, maintaining of temperature in the devicein range of 25-140° C.—24.

As an agitator of oxygen-containing gas discharge, an air compressor canbe used, as an agitator of catalyst solution supply from the tank—ametering pump, and as an agitator of catalyst solution recycling fromsulfur-separating unit—a regular pump can be used.

Below, the essence and advantages of the developed technical solutionare discussed in examples of practical implementation.

Example 1

Synthesis of catalyst C1. Into a retort, at a room temperature, 10 ml ofethyl alcohol, 100 ml of octane, 0.2-1 g of CuCl₂.2H₂O and 0.5-3 g ofamine (benzylamine, cyclohexamine, pyridine) are put. The contents ofthe retort are mixed until cupric chloride dissolves completely. Thiscomposition of the catalyst is disclosed in (RU, patent No. 2405738,issued 27 Apr. 2010).

Example 2

Synthesis of catalyst C2. Into a retort, at a room temperature, 100 mlof ethyl alcohol, 20 ml of water, 20 ml (0.25 moles) ofdimethylformamide (DMFA), and 15 g (0.09 moles) of CuCl₂.2H₂O are put.The contents of the flask are mixed until cupric chloride dissolvescompletely. This composition of the catalyst is known from (RU, patentNo. 2398735, issued 10 Sep. 2010), however, even before the scientificresearch being a basis of current invention was finished, no data ondemercaptanization capabilities of the said catalyst had been known.

Example 3

Synthesis of catalyst C3. Into a retort, at a room temperature, 100 mlof alcohol as solvent, 8-60 g of amine-dimethylformamide (DMFA) mixture,1.5-14 g of CuCl₂.2H₂O are put. The contents of the flask are mixeduntil cupric chloride dissolves completely.

Example 4

Gas purification involving catalyst C1. The gas is purified with use ofthe device and the process that are claimed as the current invention,but C1 known from (RU, patent No. 2405738, issued 27 Apr. 2010) is usedas the catalyst.

Non-aqueous organic solvent and catalyst C1 synthesized as in Example 1are put into the reactor. The gas supplied into the reactor contains0.1% vol. of hydrogen sulfide, 0.05% of mercaptan sulfur and 0.06% vol.of oxygen. The solution temperature is 25° C. The output gas contains,according to potentiometric titration results, 40 ppm and 50 ppm ofhydrogen sulfide and mercaptan respectively. Conversion of hydrogensulfide and mercaptan is 95.5 and 91% respectively.

Thus the device and the process claimed as the current invention evenwith use of a known catalyst composition (known from RU, patent No.2405738, issued 27 Apr. 2010) provide conversion rate of hydrogensulfide and mercaptan into sulfur and disulfides not more than 95.5%.

Example 5

Gas purification in accordance with current invention claim usingcatalyst C2. Non-aqueous organic solvent and catalyst C2 are put intothe reactor. The gas supplied into the reactor contains 1% vol. ofhydrogen sulfide, 0.05% SH and 0.5025% vol. of oxygen. The solutiontemperature is 25° C. The output gas contains, according topotentiometric titration results, 60 ppm of hydrogen sulfide and 60 ppmof mercaptan. Conversion of hydrogen sulfide and mercaptane is 99.4

88% respectively.

Thus examples 4 and 5 illustrate that even using of non-optimal catalystcomposition the device and process claimed as current invention providehydrogen sulfide conversion of 95.5-99.4% and mercaptan conversion of88-91%.

Examples 6-24

Gas purification using catalyst C3 that utilizes the proposed process,catalyst and device.

Non-aqueous organic solvent and catalyst C3 with content of 0.001-100%are put into the reactor. The gas supplied into the reactor contains0.1-1.8% vol. of hydrogen sulfide, 0.05-0.5% of mercaptans and0.075-1.15% vol. of oxygen. The solution temperature is 20-40° C. Theoutput gas according to potentiometric titration contains 10-0.001 ppmof hydrogen sulfide and 0.001-20 ppm of mercaptans. The conversion ofhydrogen sulfide is 99.8-99.9999%, of mercaptan—98-99.9999%. Theexperiment results with use of different catalysts C1-C3 are shown inTable 1.

TABLE 1 content. % mas. [H₂S] [RSH] Amine + Cu + in, % out, in, % out,Catalyst amide Fe vol. ppm vol ppm 4 C¹ 93 7 0.1 40 0.05 50 5 C2¹ 56 441 60 0.05 60 6 C3² 60 40 1 10 0.05 10 7 C3² 70 30 1 10 0.05 10 8 C3¹ 8020 1.8 8 0.05 10 9 C3¹ 85 15 0.5 4 0.05 10 10 C3^(1,3) 94 6 0.5 3 0.1 1011 C3^(1,3) 93 7 1.0 2 0.5 4 12 C3^(1,4) 92 8 1.0 2 0.5 3 13 C3^(2,5) 919 1.0 0.01 0.5 0.01 14 C3^(3,6) 90 10 0.1 0.001 0.1 0.001 15 C3^(1,7) 7030 1.0 0.01 0.5 0.01 16 C3^(2,4) 50 50 1.0 0.001 0.5 0.001 17 C3^(3,7)30 70 0.1 0.001 0.1 0.001 18 C3^(1,5) 10 90 0.5 0.001 0.3 0.001 19C3^(2,6) 5 95 0.5 0.01 0.5 0.01 20 C3³ 2 98 0.1 0.02 0.1 0.01 21 C3¹ 199 0.3 0.001 0.1 0.001 22 C3¹ 50 50 0.8 0.002 0.3 0.004 23 C3^(3,6) 5050 0.8 0.003 0.3 0.001 24 C3^(3,7) 50 50 0.8 0.001 0.3 0.002 Solvents:¹alcohol, ε = 20.4, 24.6, 3.7; ²glycol, ε = 37.7; ³mixture of alcoholand/or glycol with others, ε = 28.2; 34.8; 36.0; 38.0; ⁴DMFA, ε = 36.7or amine or amide; ⁵dimethylsulfoxide, ε = 46.4; ⁶alcohol + hydrocarbon;⁷alcohol + glycol + hydrocarbon

In frame of current work, the following results were discovered:

-   -   Using catalyst C1 with device and process claimed as current        invention provide insufficient conversion of hydrogen sulfide        and mercaptans, 95.5% and 91% respectively.    -   Using catalyst C2 with device and process claimed as current        invention provides not only desulfurization as in U.S. Pat. No.        2,398,735, issued 10 Sep. 2010, but also demercaptanization.        Mercaptan conversion proves to be 88%.    -   The catalyst proposed in current application catalyzed oxidation        of both hydrogen sulfide and mercaptans with high degree of        conversion, see Table 2.

Conversion of hydrogen sulfide and mercaptans in Examples 6-14 is shownin Table 2.

TABLE 2 No. conversion, % 6 7 8 9 10 11 12 13 14 H₂S 99.0 99.9 99.9699.8 99.9 99.9 99.98 99.999 99.9999 RSH 98.0 98.0 98.0 98.0 99.8 99.999.9 99.99 99.9999

Results of gas purification by proposed process and with proposed deviceand catalyst C3 with different ratio of amine/amide/transition metal areshown in Table 3. The conditions of experiment are similar to those ofexperiments No. 6-24.

TABLE 3 [H₂S] [RSH] Content, % mas. in, % out, in, % out, No. catalystamine amide metal vol. ppm vol. ppm 25 C3 89 10 1 1 10 0.1 10 26 C3 4550 5 1 10 0.1 10 27 C3 40 50 10 1 4 0.1 6 28 C3 10 70 20 1 4 0.1 6

Results of gas purification by proposed process and with proposed deviceand catalyst C3 in various solvents with ratio of amine/amide/transitionmetal=4:5:1 are shown in Table 4. The conditions of experiment aresimilar to those of experiments No. 6-24.

TABLE 4 [H₂S] [RSH] in, out, in, out, catalyst solvent % vol. ppm % vol.ppm C3 octane 1 4 0.1 6 C3 naphtha 1 10 0.1 10 C3 petrol 1 10 0.1 10

Results of gas purification by proposed process and with proposeddevice, with different content of catalyst C3 are shown in Table 5. Theconditions of experiment are similar to those of experiments No. 6-24.

TABLE 5 [C3], [H₂S] [RSH] No % vol. in, % vol. out, ppm in, % vol. out,ppm 29 0.001-0.5  1 10 0.1 12 30 1-5 1 4 0.1 6 31 10 1 0.001 0.1 0.01

Results of gas purification where the gas has different content ofmethane, ethane, C₃₊ by proposed process and with proposed device andcatalyst C3 are shown in Table 6. The conditions of experiment aresimilar to those of experiments No. 6-24.

TABLE 6 [H₂S] [RSH] content, % vol. in, % out, in, % out, No. catalystC₁ C₂ C₃₊ vol. ppm vol. ppm 32 C3 85 12 3 1 10 0.1 10 33 C3 74 22 4 1 100.1 10 34 C3 100 1 10 0.1 10 35 C3 95 5 1 4 0.1 5

The examples provided confirm that the stated technical result isachieved, yet they do not show the limits of proposed technicalsolution.

It will be understood that the system and method may be embodied inother specific forms without departing from the spirit or centralcharacteristics thereof. The present examples and embodiments,therefore, are to be considered in all respects as illustrative and notrestrictive, and the system method is not to be limited to the detailsgiven herein.

What is claimed is:
 1. A catalyst for desulfurization/demercaptanizationof gaseous hydrocarbons, that is a mixture of ferric and cupricchlorides, amines, and amides in non aqueous solvents with dielectricconstant 20<ε<80 or in their mixture with hydrocarbons.
 2. The catalystas in claim 1, wherein said amines are benzylamine, cyclohexylamine andpyridine.
 3. The catalyst as in claim 1, wherein said amines arebenzylamine.
 4. The catalyst as in claim 1, wherein said amines arecyclohexylamine.
 5. The catalyst as in claim 1, wherein said amines arepyridine.
 6. The catalyst as in claim 1, wherein said amines arebenzylamine, cyclohexylamine or pyridine.
 7. The catalyst as in claim 1,wherein said amides are dimethylformamide.
 8. A catalyst fordesulfurization/demercaptanization of gaseous hydrocarbons, that is amixture of ferric or cupric chlorides, amines, and amides in non aqueoussolvents with dielectric constant 20<ε<80.
 9. The catalyst as in claim8, wherein said amines are benzylamine, cyclohexylamine or pyridine. 10.The catalyst as in claim 8, wherein said amides are dimethylformamide.11. A catalyst for desulfurization/demercaptanization of gaseoushydrocarbons, that is a mixture of ferric or cupric chlorides, amines,and amides in their mixture with hydrocarbons.
 12. The catalyst as inclaim 11, wherein said amines are benzylamine, cyclohexylamine orpyridine.
 13. The catalyst as in claim 11, wherein said amides aredimethylformamide.